US2894057A - Submarine cables having anti kink armouring - Google Patents

Description

July 7, 1959 A. 1.. MEYERS SUBMARINE CABLES HAVING ANTI KINK ARMOURING Filed Oct. 10, 1955 United States Patent i SUBMARINE CABLES HAVING ANTI KINK ARMOURING Arthur Lennox Meyers, Herne Hill, London, England,

assignor to Submarine Cables, Limited, London, England, a company of Great Britain Application October 10, 1955, Serial No. 539,561

Claims priority, application Great Britain October 15, 1954 5 Claims. (Cl. 174-408) This invention relates to submarine cables and is concerned with an improved construction of armouring for use therewith.

It has long been recognised that in a deep-sea submarine cable having a single layer of armouring wires there is a tendency to produce deletereous effects due to the twisting of the cable, and particularly is this so in a cable having repeater apparatus or the like at spaced intervals, since at those sections of the cable on each side of the repeater apparatus it will be found that the turns in the cable tend to pile up under longitudinal tension, which 1 occurs during the operations of laying and recovery by the cable ship, with the result that kinks may be formed in the cable which may cause electrical faults or even complete breakage.

Trouble is liable to occur particularly when picking up cable connected to a repeater during repair or recovery operations. At this time the armour wires will be subjected to a heavy load due to the weight of the suspended cable and perhaps also of an attached repeater, and consequently axial twisting occurs. Provided the longitudinal tension were steady, this twisting of itself might not have any serious consequence; but in practice it is not steady. For example, the rise and fall of the ship in an ocean swell causes variation of the tension, and waves of augmented and diminished tension travel down the cable, with consequent variations in the degree and rate of axial twist. The repeater, owing to friction against the seabed, or, when suspended to its bulk and mass, partially interrupts the waves of axial twist. The result is that under momentarily relaxed tension near the bottom, there is a tendency for the cable to be thrown into turns or coils, and for the turns to accumulate at or near the repeater. Under continued tension, as the ship rises or the cable continues to be picked up, these turns may be drawn out into kinks, which may cause electrical faults. Breakage of the cable under the full tension as the kinks approach the surface may make it impossible to recover the repeater.

In order to overcome this difiiculty it has been proposed to provide a double layer of armouring wires, the wires of the outer layer being helically applied in the opposite direction to the wires of the inner layer, the purpose being to ensure that the tendency of one layer to cause twisting is balanced by that of the other layer to cause twisting in the opposite direction.

It will be appreciated moreover, that the provision of two layers of armouring wires for the whole length considerably increases the cost of production of the cable quite apart from the appreciable increase in weight, which is undesirable.

It might be considered that an appreciable length of double armoured cable could be used in the vicinity of the repeaters spliced to a single armoured cable which comprises the majority of the length of the cable between repeaters. The objection to such an arrangement is that the sudden change in the torsional properties of the cable at the junction between the two types again partially in- 'ice terrupts the waves of axial twist, and that there is then a tendency for turns to be thrown and for kinks to be formed at or near the junction.

According to the present invention in a submarine cable having an armouring and provided with repeater apparatus or other insertions the armouring comprises sections extending between each repeater apparatus or insertion in which the armouring structure remains torsionally unbalanced for the greater portion of the section but is such that in the vicinity of the repeater or insertion it is substantially balanced, the balanced and unbalanced sections being joined to one another by an intermediate armouring structure such that the change over from the balanced to the unbalanced portions is a progressive one, thereby preventing any appreciable change in torsional properties at any one place.

In practice it will result in the Waves of axial twist being progressively reduced in amplitude without serious partial interruption at any one place, so that the tendency to throw turns and form kinks is eliminated. Moreover this benefit is obtained without undue increase in the overall cost of the cable.

The desired graduation of the torsional properties of the cable can be obtained by continuing the armour Wires of the single armoured cable without alteration up to the repeater and by applying over them a second layer of armour wires in the opposite direction, the angle of lay of the wires with respect to the axis and/ or the diameter of the wires and/ or the number of wires in the second and outer layer being progressively increased until substantial torsional balance is obtained in the double armoured cable next to the repeater. Alternatively, the desired graduation can be obtained by progressively altering the angles of lay and/or the numbers and/or the diameters of wires in both the inner and outer layers.

The distance over which the progressive graduation in the torsional properties of the cable is eliected may be as short as fathoms, or may extend to 1000 fathoms or more. It is desirable to have a considerable length, say 100 fathoms or more of substantially balanced double armoured cable next to the repeater.

The invention is illustrated in the accompanying drawing in which Fig. l is a diagrammatic view of a submarine cable provided at intervals with repeater apparatus,

Fig. 2 is a side elevation, on a non-uniform longitudinal scale, a section of cable having progressively graduated torsional properties,

Fig. 3 is a transverse section through the substantially torsionally balanced cable next to a repeater and approximately on the line III-III of Fig. 1.

In Fig. l of the drawings S indicates a length of cable joining two repeater apparatus indicated generally at R R which it will be understood occur at regular intervals throughout the submerged length of the cable.

Referring now to Figs. 2 and 3 of the drawings there is shown a submarine cable wherein the cable conductors form a coaxial structure, comprising an inner copper conductor C, insulated by a layer A of thermoplastic insulation material, such as polyethylene, outside which is an outer conductor B consisting of a layer of copper tapes applied helically and held in position by a copper binding tape D. As shown in section in Fig. 3, the cable core is surrounded, in accordance with standard practice, by an inner serving 15 of jute yarn over which is the inner layer of armour wires 16, consisting in this case of 21 galvanised steel wires each of 0.095" diameter, applied helically with a left hand lay of 16''. This layer of armour is continued unchanged from the repeater R which is to the left of Fig. 1, through the special section shown in Fig. 1, to form the single armour of the majority of the cable length, to the right of Fig. l, and up to the next repeater, R and through the entire length of the cable between repeaters.

Referring again to Fig. 3, the layer of armour wires 16 is surrounded by another serving 17 of jute yarn secured by a whipping of jute (not shown). Over the jute serving layer 17 is the outer layer of armour wires 18 which extends up to the repeater R and constitutes with the inner layer 16 of armour wires the double armouring. The outer layer in this case consists of 34 galvanised steel wires each of 0.072 diameter, applied helically with a right hand lay of 26". Finally this outer layer 18 of armour is covered by an outer serving 19 consisting of two layers of jute yarn applied in opposite directions. As shown in Fig. 3, each armour wire may be protected from corrosion by an individual covering of tar compound held in position by a fabric tape, or by an individual coating of extruded plastic material such as polyvinylchloride. As a further protection the cable is completed with a coating of tar compound overall.

The number, dimensions and lays of the armour wires are such that the fully double armoured cable next to a repeater is substantially torsionally balanced, so that it does not twist axially when subjected to longitudinal tension.

The novel feature of the invention is illustrated diagrammatically in Fig. 2, which shows how the torsional properties of the cable may be progressively graduated in steps or stages from the non-twisting fully double armoured cable to the left of Fig. 1 to the twisting single armoured cable to the right of Fig. 2. Thus section 1, which may have a length of 100 fathoms or more, shows the fully double armoured cable next to a repeater. At the beginning of section 2, which represents a substantial length of cable for example 25 fathoms in Example No. II or 80 fathoms in Example No. III, certain of the wires, as indicated at 2A in the outer layer of armour are cut and thus terminated i.e. they are omitted from, the outer layer. This process is continued in sections 3, 4 and 5, where the terminated wires are indicated respectively at 4A and 5A both of which represent substantial lengths of cable, and in further sections not shown in the drawing, until in section 9 only a few wires remain in the outer layer. These few wires are omitted at the beginning of section 10, so that the cable then contains only a single layer of anmour wires. The gaps left by the removal of wires are filled with jute yarn as indicated 2B in section 2 and 3B in section 3. The cut ends are secured by bindings 20. The outer serving 19 is carried over the special section of cable, and is tapered down at the single armoured end, where it may be bound down or continued to form the outer serving of the single armoured cable.

In accordance with the invention, a special section of cable such as illustrated and just described, is provided on each side of each repeater to be laid in deep water.

Example I A short length of cable, made up for test purposes and all of which was armoured with 16/ 13 E.W.T. wires, had applied to it at one end, a second and outer layer of armouring with the wires arranged in opposite lay, the wires in the outer layer being reduced at intervals so as to give the following reductions:

28/15 wires for 15 yds. reduced to 21/15 wires for ten yds., reduced to 14/15 wires for ten yds., finally reduced to 7/15 wires for ten yds.

Tests on this short length of cable demonstrated that the progressive graduation in the number of Wires in the outer armour prevented any sudden change in the torsional properties of the cable.

Examples II and III set out below show examples of designs, in accordance with the invention, of tapered double armoured cable intended for use at sea. In both these cases the inner layer of armour consists of 21 steel wires each of 0.095" diameter, with a left hand lay of 16", continued unchanged to form the single armour of the majority of the cable between repeaters; and the outer layer of armour, at the fully double armoured end next to a repeater, consists of 34 steel wires each of 0.072" diameter applied with a right hand lay of 26". The angle of lay of the outer layer is not changed, but the number of wires in the outer layer is progressively reduced in 7 steps in Example II and in 11 steps in Ex ample III.

Example 11 Length fathoms Number Then remove wire numbers of wires Example III Length fathoms Number Then remove wire of wires numbers i The wires are removed in as symmetrical a manner as is conveniently practicable, as shown in the above examples. The ends of the cut wires are bound down securely, and the spaces resulting from the removal of the wires are filled with jute. A normal outer serving of jute is carried over the complete taper, and the cable is finished with a normal coating of tar compound.

Although in the examples given above the torsional graduation is obtained in steps by altering the number of wires in the outer layer, it is clear, as has already been stated that, in accordance with the invention, the desired graduation may be obtained by altering, instead or in addition, the angle of lay and/or the diameter of the wires. It might be thought that the best result would be obtained by a continuous alteration of the angle of lay, as this would give a continuous graduation instead of a graduation in steps; however, not only is this difficult to carry out in practice, but also such refinement has not been found necessary.

Although the invention has been described and illustrated in relation to a cable in which the tensile elements are wires, it is clear that the desired torsional graduation may similarly be obtained with tensile elements of shapes other than circular.

It will be understood that the invention is also applicable to other insertions, such as loading coils, which may cause similar mechanical diflicuities.

What is claimed is:

l. A submarine cable comprising a conductor, an insulation for the conductor and an armouring surronnding the insulated conductor, and in which electrical repeater apparatus are provided at intervals in the cable length, in which the armouring comprises a stranded inner layer of wires applied continuously over those sections of the cable between the repeater apparatus and adjacent to the ends of each of such repeater apparatus, an outer stranded layer of wires, the wi res in the outer layer being of opposite lay to the wires of the inner layer and extending from the respective repeater apparatus towards the next repeater apparatus to ,provice a double armoured cable portion adjacent to the repeater apparatus, but

terminating short of the next adjacent repeater apparatus to leave an intervening single layer armoured cable section, the number of wires in one of said layers decreasing in stages each at least ten yards long from the repeater apparatus to the adjoining single layer armoured portions of the cable, whereby the tendency of the cable to twist increases progressively in stages from a substantially zero tendency to twist in the fully double armoured portions adjacent to the repeater apparatus to the single armoured portions of said cable.

2. A submarine cable as claimed in claim 1 in which the inner layer of armour wires in the double armoured portions of the cable continues unchanged throughout the length extending between repeater apparatus to provide the armour in the single armoured portion and in which the number of wires in the outer layer at the start of each stage is reduced.

3. An armoured submarine cable in accordance with claim 1 in which the number of wires in both layers at the start of each stage is reduced.

References Cited in the file of this patent UNITED STATES PATENTS 1,873,798 Varney Aug. 23, 1932 2,041,269 Smith et a1. May 19, 1936 2,414,045 Kitselman Jan. 7, 1947 2,754,351 Horn July 10, 1956 OTHER REFERENCES Transactions of The A.S.E.E., vol. 70, Part 1, pages 565-566, 1951, copy in Division 69, 174-701

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